Power takeoff for an electric vehicle

ABSTRACT

A power take-off for an electric vehicle. The power take-off includes a variable speed electric motor for driving at least one wheel of the vehicle. A transmission, including a neutral state, coupled to the electric motor. An auxiliary output shaft is coupled to the transmission. When the transmission is in the neutral state, the auxiliary output shaft will operate at a speed independent of wheel speed and dependent on the electric motor speed. When the transmission is operably engaged in other than the neutral state, the auxiliary output shaft will operate at a speed related to both the electric motor speed and the wheel speed.

FIELD

The present invention relates generally to hybrid electric vehicles, andmore particularly to a power take-off coupled to an axle for an electricvehicle.

BACKGROUND

In a conventional electric vehicle, a prime mover such as a dieselengine, is used to drive an electric generator or alternator whichsupplies electric current to a plurality of electric motors. Theelectric motors typically are coupled to wheel sets, in line, on thevehicle. The vehicles that utilize this type of hybrid electric motorsare typically railroad locomotives.

The prime mover drives the generator/alternator that typically producesan AC current that is then fully rectified with resulting DC current andvoltage being distributed to current converters coupled to the tractionmotors. Such systems are highly integrated with each of the componentstypically designed and manufactured to operate with the other componentsin the overall system. In other words, “off the shelf” components arenot readily adaptable for use in the initial design or ongoingmaintenance of such vehicles. Further, such vehicles have multiplecomponents associated with the change of AC to DC to AC power.Maintenance of such systems is expensive since specific components mustbe used.

In the use of hybrid drives for such vehicles, it is often necessary toadd support systems that require a source of power to operate.Typically, these systems are centrally mounted on the vehicle andrequire the routing of specialized, pressurized, conduits to specificpoints around the vehicle. Conventional sources of auxiliary power aretypically an internal combustion engine operated generator or a motorgenerator set. Such additional components and equipment add cost to thevehicle and take up space on the vehicle.

Thus there is a need for a power take-off for a vehicle that does notrequire an additional engine. There is a further need for a method toprovide power to an auxiliary apparatus mounted on a vehicle utilizingthe traction motor of the vehicle.

SUMMARY OF THE INVENTION

There is provided a power take-off for an electric vehicle. The powertake-off includes a variable speed electric motor for driving at leastone wheel of the vehicle. A transmission, including a neutral state,coupled to the electric motor. An auxiliary output shaft is coupled tothe transmission. When the transmission is in the neutral state, theauxiliary output shaft will operate at a speed independent of wheelspeed and dependent on the electric motor speed. When the transmissionis operably engaged in other than the neutral state, the auxiliaryoutput shaft will operate at a speed related to both the electric motorspeed and the wheel speed.

There is also provided a method for providing power to a tool mounted ona vehicle utilizing an electric motor of the vehicle, with the electricmotor coupled to an axle to transmit power to a vehicle wheel. Themethod comprises the steps of providing a power take-off (PTO) apparatushaving a gear train. Coupling the PTO gear train to the electric motor.Providing a planetary annulus gear. Coupling the planetary annulus gearto the axle with the planetary annulus gear configured to move between afirst position and a second position. In the first position, the PTOwill move at a speed independent of wheel speed and dependent onelectric motor speed and in the second position, the PTO will move at aspeed related to both electric motor speed and wheel speed.

There is further provided a vehicle comprising a vehicle supportstructure. A principal power unit supported by the structure, whereinthe principal power unit is not a battery. An electric AC power busincluding at least two phase conductors, wherein the phase conductorsare coupled to the principal power unit. A power storage unit coupled tothe AC power bus. A self-contained axle module coupled to the vehiclesupport structure and an electric motor. A vehicle controller coupled tothe self-contained axle module and the AC power bus. A data bus coupledto the self-contained axle module and vehicle controller. A motor drivecontroller unit coupled to the electric motor and to the vehiclecontroller to communicate signals to the vehicle controller such thatone of the speed and torque of the electric motor is controlled basedupon the signals. An output shaft is coupled to the electric motor. Afirst wheel end assembly is coupled to the output shaft and a secondwheel end assembly is coupled to the output shaft. A power take-off iscoupled to the axle module. The power take-off includes a transmission,including a neutral state, coupled to the electric motor. An auxiliaryoutput shaft is coupled to the transmission, wherein when thetransmission is in the neutral state, the auxiliary output shaft willoperate at a speed independent of wheel speed and dependent on electricmotor speed. When the transmission is operably engaged in other than theneutral state, the auxiliary output shaft will operate at a speedrelated to both the electric motor speed and wheel speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an electric vehicle according to anexemplary embodiment.

FIG. 2 is a partial perspective view of an exemplary embodiment of avehicle including a self-contained axle module coupled to a vehiclesupport structure of the vehicle.

FIG. 3 is a cross section of a power take off coupled to a transmissionmounted in a housing of an axle module and coupled to an electric motorof a hybrid vehicle.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 is a schematic diagram of an electric vehicle 10 according to anexemplary embodiment. An electric vehicle is a vehicle that useselectricity in some form or another to provide all or part of thepropulsion power of the vehicle. This electricity can come from avariety of sources, such as stored energy devices relying on chemicalconversions (batteries), stored electrical charge devices (capacitors),stored energy devices relying on mechanical stored energy (e.g.flywheels, pressure accumulators), and energy conversion products. Ahybrid electric vehicle is an electric vehicle that uses more than onesources of energy, such as one of the electrical energy storage devicesmentioned above and another source, such as an internal combustionengine. By having more than one source of energy some optimizations inthe design can allow for more efficient power production, thus one canuse power from different sources to come up with a more efficient systemfor traction. The electric vehicle 10 can be used to implement electricvehicles in general and/or hybrid electric vehicles in particular. Theelectric vehicle 10 can implement a number of different vehicle types,such as a fire-fighting vehicle, military vehicle, snow blower vehicle,refuse handling vehicle, concrete mixing vehicle, etc.

In the illustrated embodiment, the electric vehicle 10 includes anengine 18, a generator 20, an electric power converter 24, an energystorage device 26, a plurality of electric motors 28, a plurality ofdrive controllers 30, a vehicle controller 34. Electric vehicle 10optionally includes an energy dissipation unit 32. The generator 20, thedrive controllers 30, and the electric power converter 24 areinterconnected by a power bus 42, such as an AC or DC power bus.Electric vehicle 10 is generally configured to use a combination of theengine 18 and the generator 20 to provide braking capability and todissipate excess electrical power generated by the electric motors 28during regenerative braking.

The engine 18 is preferably an internal combustion engine, such as adiesel engine configured to both provide mechanical power to thegenerator 20 and to receive mechanical power from generator such thatmay function as a mechanical engine brake or air compressor. Thegenerator 20 is coupled to the engine 18 and may be configured tofunction as both generator configured to provide AC or DC power, and asa motor configured to receive electrical power and provide mechanicalpower to the engine 18.

The electric power converter 24 is coupled to the energy storage device26 and is configured to convert the electrical power generated by thegenerator 20, or by the electric motors 28 during regenerative braking,to the energy mode required by the energy storage device 26. Forexample, according to an exemplary embodiment, the electric powerconverter is configured to convert AC power generated by the generator20 to DC power and transfer such converted power to the storage device26. The electric power converter 24 may also convert the energy storedin the energy storage device 26 back to the energy mode of generator 20to augment and supplement the power generated by generator 20 over thepower bus 42. The energy storage device 26 may be electric capacitors,electrochemical capacitors or “ultracapacitors,” storage batteries, aflywheel, or hydraulic accumulators.

The electric motors 28 are appropriately sized electric motors, whichmay be AC or DC electric motors. The electric motors 28 are configuredto receive electrical power from the power bus 42 in order to provide amechanical energy output to a wheel or axle. The electric motors 28 arealso configured to receive mechanical energy from the wheel or axleduring regenerative braking in order to generate electrical power ontothe power bus 42.

The drive controllers 30 are coupled to each electric motor 28 and areconfigured to control the operation of each electric motor 28. Morespecifically, the drive controllers are configured to allow the electricmotors 28 to either receive electrical power from the power bus 42 inorder to provide a mechanical energy output to a wheel or axle, or toreceive mechanical energy from the wheel or axle during regenerativebraking in order to generate electrical power onto the power bus 42.

The vehicle controller 34 is coupled to the engine 18, the generator 20,the electric power converter 24, and the drive controllers 30 via a databus network 76. The vehicle controller 34 is generally configured tocontrol the operation of the engine 18, the generator 20, the electricpower converter 24, the energy storage device 26, the plurality ofelectric motors 28, and the plurality of drive controllers 30. Morespecifically, the vehicle controller 34 is configured to assist incontrolling the distribution of electrical power on the power bus sothat the flow of electrical power from generator 20 may be reversed toprovide braking capability, and so that excess electrical powergenerated by the electric motors 28 during regenerative braking isrouted back to the generator 20 so that it may be dissipated.

The optional energy dissipation unit 32 is typically a resistive elementthrough which electrical power generated by the electric motors 28during regenerative braking is dissipated as heat if the electricalpower exceeds the capacity of the energy storage device 26. Preferably,electric vehicle 10 is configured such that the excess electrical powergenerated by the electric motors 28 during regenerative braking issufficiently dissipated through engine 18 and generator 20.

In conventional vehicles and particularly in vehicles having a hybridelectric drive, it is often necessary to add support systems such aspressurized lubrication and supplemental cooling systems. Such systemstypically are centrally mounted on the vehicle and require the routingof pressurized oil lines throughout the vehicle. The elimination of orlimiting the number of such specialized conduit lines being routedthrough the vehicle, results in additional space for other componentsand truck parts. A self-contained axle module 50 for the vehicle 10,which typically includes a lubrication pump, the oil filter, and heatexchanger at the axle and integrating such components into aself-contained axle module minimizes the conduit routings mentionedabove.

A self-contained axle module 50 can be mounted or coupled to the vehicle10 support structure 12 at any convenient position determined by themanufacturer or user of the vehicle 10. Also, because of the modularconfiguration, a self-contained axle module 50 can be easily removed andreplaced for maintenance or repairs. The self-contained axle module 50only has to be coupled to the source for electrical power such as theprincipal power unit and generator 18, 20 and the electric AC power bus42. It should be understood that other sources of power, as describedabove, can be coupled to the self-contained axle module 50 to providethe necessary electrical power to operate the electric motor 28, asdescribed below. In addition to coupling electric power to theself-contained axle module 50, a control signal, through a data bus 76network provides the necessary control and feedback signals foroperation of the axle. It is also contemplated that supplemental coolingmay be required because of the environment or operating conditions ofthe self-contained axle module 50 and therefore supplemental coolingsource can also be coupled to the axle.

The housing 56 can be composed of any suitable material, such as iron,steel, or aluminum and can be cast and machined as designed by themanufacturer. The housing 56 includes a sump portion in the lowest areaof the housing 56. The housing 56 in addition to the componentsdescribed below also houses a transmission 58 which transmits force fromthe electric motor 28 to the output shaft 60 and to a power take-off 88.The transmission 58 may include several types of gears such as planetarygears, sprocket gears, bevel gears or the like with selected gear ratiosas determined by the manufacturer and operator of the vehicle 10.

The power take-off 88 includes a power take-off (PTO) housing 74 mountedon the housing 56 and coupled to the transmission 58 and an auxiliaryapparatus 75, such as a tool 77 (See FIG. 3.). The transmission 58includes a primary drive gear 90 which is coupled to the motor drivegear 91. The motor drive gear 91 transmits rotational power from theelectric motor 28. The primary drive gear 90 is coupled to the PTO geartrain 100 and to the bevel gear differential assembly 65. Thetransmission 58 is in a neutral state when a secondary reductionplanetary annulus 96 is moved to a neutral position such that it is notcoupled to the primary drive gear 90. When the secondary reductionplanetary annulus 96 is in the neutral position, the tool 77 willoperate at a speed other than the speed of the vehicle. In other words,it will operate at the speed proportional to the speed of the electricmotor 28. When the secondary reduction planetary annulus 96 is moved toa position other than the neutral position, for example, when it iscoupled to the primary drive gear 90, the subsystem apparatus 75 willoperate at a speed related to both the electric motor 28 speed and thewheel speed since it is coupled to the output shaft 60 of the axlemodule 50 of the vehicle 10. The secondary reduction planetary annular96 can be moved by an actuator, for example, a fluid cylinder (pneumaticor hydraulic) or an electric apparatus, such as a solenoid.

The transmission 58 also includes a secondary reduction planetarycarrier 95, a secondary reduction planetary planet gear 97 and asecondary reduction planetary sun gear 98. It should be understood thatother types of gearing configurations are contemplated for thetransmission 58. It should also be understood that the housing 56 andthe power take-off housing 74 can be integrally formed to house both thepower take-off gear train 100 and the transmission 58.

The tool 77 can be any type of tool that requires mechanical powertransmission, for example, a hydraulic pump 78 or a drive shaft, apulley for a belt drive or similar apparatus can be coupled to the powertake-off 88.

It should also be understood that the transmission 58 can be geared forat least two speeds, however, any other number of gear ratios can beutilized to obtain any number of appropriate and convenient speeds forpurposes of powering the power take-off 88 (also referred to as asubsystem power source).

A method for providing power to a subsystem apparatus, such as a tool 77is accomplished by mounting a power take-off 88 on a vehicle utilizingan electric motor 28 of the vehicle 10. The electric motor 28 is coupledto an axle module 50 to transmit power to a vehicle wheel 14. The methodincludes the steps of providing a power take-off (PTO) apparatus 88having a PTO gear train 100. Coupling the PTO gear train 100 to thetraction motor 28. Providing a planetary annulus gear 96 and couplingthe planetary annulus gear 96 to the axle 50 with the planetary annulusgear 96 configured to move between a first position and a secondposition wherein in the first position, the PTO 88 will move at a speedrelated to the speed of the vehicle 10 and in the second position, thePTO 88 will move at a speed different from the speed of the vehicle 10.The PTO 88 is always driven as a function of the electric motor 28 speedwith the proviso that the PTO 88 speed may be related to the vehiclespeed.

Control of the secondary reduction planetary annulus 96 is maintained bya fluid cylinder such as an air cylinder. It is also contemplated that ahydraulic cylinder or an electric apparatus, such as a solenoid can beutilized to move the secondary reduction planetary annulus 96 from afirst position to a second position.

The PTO 88 can be used to drive the tool 77, such as a pump 78, and topower other equipment associated with the vehicle 10. The PTO can beconfigured to operate at a speed related to the vehicle speed or tofunction at a speed other than the speed of the vehicle. The electricmotor 28 provides power to the PTO through an associated PTO gear train100 and can be coupled or uncoupled to the output shaft 60 of theself-contained axle module 50.

The tool 77 such as a pump 78 can be utilized as a high volume waterpump mounted on one of the axle modules 50 of the fire truck or airportcrash truck. As an example, one of the axle modules 50 can be configuredto move the vehicle 10 while another axle module 50 is configured topower the tool 77, such as the water pump with the PTO 88.

According to another alternative embodiment, the tool 77 powered by thepower take-off apparatus 88 can be a power generator where therotational mechanical energy of the electric motor 28 is converted intoelectrical energy to power additional auxiliary systems. Sucharrangement can be configured as described above, where one axle module50 is configured to move the vehicle 10 and another axle module 50 isconfigured to power the power generator either when the vehicle 10 ismoving or while the vehicle 10 is stopped.

Several alternative embodiments have been described with reference tothe power take-off apparatus 88, however, the invention is not limitedto the described embodiments. Any power take-off system that utilizesthe rotational mechanical energy supplied by the electric motor 28 iswithin the scope and spirit of the invention.

It is also contemplated that the vehicle 10 may also include a pluralityof independent suspension assemblies 86 which independently suspends oneof the wheel end assemblies relative to the vehicle support structure12′.

For purposes of this disclosure, the term “coupled” means the joining oftwo components (electrical or mechanical) directly or indirectly to oneanother. Such joining may be stationary in nature or movable in nature.Such joining may be achieved with the two components (electrical ormechanical) and any additional intermediate members being integrallyformed as a single unitary body with one another or with the twocomponents or the two components and any additional member beingattached to one another. Such joining may be permanent in nature oralternatively may be removable or releasable in nature.

The foregoing description of embodiments has been presented for purposesof illustration and description. It is not intended to be exhaustive orto be limited to the precise forms disclosed, and modifications andvariations are possible in light of the above teachings. The embodimentswere chosen and described in order to explain the principles of thesubsystem power source and its practical application to enable oneskilled in the art to utilize the various embodiments and with variousmodifications as are suited to the particular use contemplated. It isintended that the scope of the subsystem power source be defined by theclaims appended hereto and their equivalents.

1. An electric drive axle module with a power takeoff for a vehiclecomprising: a housing; a main output shaft extending from the housingand having a first segment defining a first end and a second segmentdefining a second end; a first wheel end assembly coupled to the firstend and configured to be independently suspended relative to thevehicle; a second wheel end assembly coupled to the second end andconfigured to be independently suspended relative to the vehicle; avariable speed electric motor coupled to the housing; a transmissiondisposed within the housing and including a neutral state, thetransmission coupled to the electric motor and engageable with the mainoutput shaft to drive the wheel end assemblies; and an auxiliary outputshaft coupled to the transmission, wherein when the transmission is inthe neutral state, the auxiliary output shaft will operate at a speedindependent of a speed of the wheel end assemblies and dependant on theelectric motor speed and when the transmission is operably engaged inother than the neutral state, the auxiliary output shaft will operate ata speed related to both electric motor speed and the speed of the wheelend assemblies.
 2. The electric drive axle module of claim 1, whereinthe transmission is rotably mounted in a housing.
 3. The electric driveaxle module of claim 1, further comprising a power takeoff housingcoupled to the housing and at least partially enclosing the auxiliaryoutput shaft.
 4. The electric drive axle module of claim 1 wherein atool is coupled to the auxiliary output shaft.
 5. The electric driveaxle module of claim 4, wherein the tool is a pump.
 6. The electricdrive axle module of claim 1, wherein the vehicle is a hybrid electricvehicle.
 7. The electric drive axle module of claim 1, wherein thetransmission is geared for at least two speeds.
 8. A method forproviding an electric drive axle module that provides power to a toolmounted on a vehicle, the method for providing power comprising thesteps of: providing a housing; providing a main output shaft extendingfrom the housing and having a first segment defining a first end and asecond segment defining a second end; providing a first wheel endassembly coupled to the first end and independently suspended relativeto the vehicle; providing a second wheel end assembly coupled to thesecond end and independently suspended relative to the vehicle;providing a variable speed electric motor coupled to the housingproviding a power-take-off (PTO) apparatus having a gear train; couplingthe PTO gear train to the electric motor; providing a planetary annulusgear configured to move between a first position and a second position,wherein in the first position, the PTO will move at a speed independentof wheel speed and dependant on the electric motor speed and in thesecond position, the PTO will move at a speed related to both electricmotor speed and wheel speed.
 9. The method of claim 8, wherein the firstposition is a neutral position.
 10. The method of claim 8, wherein thetool is a pump.
 11. The method of claim 8, wherein the vehicle is ahybrid electric vehicle.
 12. An electric drive axle module with a powertakeoff for use with a vehicle, comprising: a housing; a main outputshaft extending from the housing and defining a first end and a secondend; a first wheel end assembly coupled to the first end and to beindependently suspended relative to the vehicle; a second wheel endassembly coupled to the second end and independently suspended relativeto the vehicle; a variable speed electric motor coupled to the housing;a transmission disposed within the housing and coupled to the electricmotor, the transmission operable in a neutral state where power is nottransmitted from the motor to the wheel end assemblies and an engagedstate where power is transmitted from the electric motor to the wheelend assemblies; and an auxiliary output shaft coupled to thetransmission, wherein when the transmission is in the neutral state, theauxiliary output shaft will operate at a speed independent of a speed ofthe wheel end assemblies and dependant on the speed of the electricmotor and when the transmission is the engaged state, the auxiliaryoutput shaft will operate at a speed related to both electric motorspeed and the speed of the wheel end assemblies.
 13. The electric driveaxle module of claim 12, further comprising a power takeoff housingcoupled to the housing and at least partially enclosing the auxiliaryoutput shaft.
 14. The electric drive axle module of claim 12, whereinthe vehicle is a fire fighting vehicle and the auxiliary output shaft iscoupled to a fire suppression water pump mounted on the vehicle.